Today, most computers do not come standard with an RS-232 9-pin serial port. This device enables you to plug your USB-only equipped computer into your Compu-Dobby I, II or III serial port. We have tested two brands (Cool Gear and Keyspan) to work well with many computer types and operating systems. These are the only two we specify or use.Comes standard with CD-ROM for installing the device driver. NOTE: The driver must be installed and properly configured for enable proper use. Additionally, the port should be set between 1 and 7.